A main area of application of the invention is in the field of brushless DC motors and other permanent magnet motors which are configured as inner rotor motors or as outer rotor motors. The invention, however, is not limited to this area and can be generally applied to any kind of electric motor or generator.
Electric motors having an inner rotor configuration have a rotor arrangement that is mounted onto the shaft and comprises one or more permanent magnets, as well as a stator arrangement made up, for example, of a number of stacked metal laminations having an annular stator back yoke and stator poles, which sometimes are called “hammer” or “tooth”, protruding inwards from the stator back yoke. Phase windings are applied to the hammers. The rotor arrangement is inserted coaxially into the stator arrangement. In the case of outer rotor motors, the rotor coaxially encloses the stator.
Before the stator hammers are wound with the phase windings of the electric machine, the hammers have to be electrically insulated. To this effect, it is known to place coil carriers made of plastic onto the hammers. It is also known to coat the hammers and the stator slots located between the hammers with a plastic coating. In the prior art, moreover, two-piece insulating bodies made of plastic are known that have a first and a second part having moldings that are adapted to the shape of the hammers and the stator slots which can be slid onto the stator on both sides in an axial direction. The two parts of the insulating body are dimensioned in the axial direction so that once they are mounted onto a stator, their moldings, adapted to the hammers and the stator slots, partly extend over the axial length of the stator slots and abut one another at their interfaces. Depending on the tolerances used during the manufacture of the two parts of the insulating body, a gap between the two parts can occur if they are shorter in total than the axial length of the stator; or it can also happen that the two parts of the insulating body overlap each other so that, due to the material thickness in the region of the overlap, an air gap between the insulating body and the stator is created when the two parts of the insulating body are longer in total than the axial length of the stator. A gap between the two parts of the insulating body can result in the hammers of the stator not being sufficiently insulated against the phase windings. Moreover, an air gap between the insulation and the stator material carries the risk that leakage current paths may be formed. Two-piece insulating bodies for stator slots which have a rebate or bevel in the region of the overlap are also known from the prior art.
In the electric machines of the prior art that have this kind of insulating body, it is common practice that after the stator has been wound, the winding heads and winding ends of the phase windings are individually bound and fixed to the stator or led away from the stator. This process is very labor intensive, the phase windings of the wound stator very often being arranged in a confused manner and it being difficult to identify exactly where the respective winding ends are led out of the stator.
It is the object of the invention to provide a device for the insulation of the stator slots of an electric machine that is simply constructed and clearly laid out and ensures perfect insulation of the stator slots.